Generally, the yarn guiding member of a yarn guiding device for knitting machine, which member is a component coming directly into contact with the running yarn, is mainly composed of a high grade steel for the sake of a high tenacity and erosion resistance.
While the guiding member of a yarn guiding device, consisting of the steel, can be used for a long period without a problem in the case of handling cotton yarns, the member can cause a hairy feathering on the knitting yarn or a breakage of the yarn owing to the wear of the area in contact with the passing yarn in the case of processing tough synthetic fiber yarns.
Thus, in recent years, a method was practised to improve the wear resistance of the yarn guiding device, wherein the inner wall of the yarn passage hole is coated with a hard film of metals or metal compounds such as chrome, titanium nitride or the like through plating process, but there was posed a problem in that the small dimension of the hole with its diameter of only about 1 mm and the shape of hole tapering toward the hole exit made an elaborate coating deep into the hole very difficult and moreover the duration life of the coating was short compared to the high preparation cost, requiring frequent replacements, whereby the efficiency of operation was extremely low.
To overcome the above-described problem, a yarn guiding member 4 of a yarn guiding device A' as shown in FIG. 7 was tried, which member was molded overall from an ordinary ceramic material excellent in wear resistance and hardness. However the product which experienced a distortion and deformation during the sintering process due to the spatial variation of shrinkage depending on the forming pressure was met with frequent breakage of the yarn guiding member, 4 when this member was firmly joined with a bracket 1 made of steel through a connecting hole 3 positioned in the upper part of the member. The sintered product was weak to impact and was also difficult to have a precise contour and smooth surface finishing to accelerate the wear of the knitting needle coming into contact with the yarn guiding member 4 up to the breakage of the needle, whereby the fed yarn is damaged to degrade the quality of the final knitgoods and sometimes even causes the stop of operation of the knitting machine.